Acidizing corrosion inhibitor



United States Patent 3,197,403 ACIDIZING CORROSION INHIBITOR Olen L. Riggs, Jr., Ponca City, Okla, assignor to Continental Oil Company, Ponca City, Okla, a corporation of Delaware No Drawing. Filed Apr. 4, 1960, Ser. No. 19,480 21 Claims. (Cl. 252-4555) This invention relates to a method for inhibiting the corrosion of ferrous metals. More particularly, this invention concerns a method for inhibiting corrosion of a ferrous metal subjected to aqueous acid environments. In narrower aspects, the present invention relates to an acidizing process for the removal of calcareous scale formations from a ferrous metal surface whereby corrosive attack of the metal substrate is inhibited.

In many industrial practices, the need to contact ferrous metal surfaces with strong acidic agents constantly arises. Particularly under numerous industrial circumstances equipment fabricated of ferrous metals such as boilers and the like often accumulate scale formations which must be periodically removed in order to maintain the efficiency of the equipment involved. For example, it is common within the petroleum industry to utilize heater tubes in contact with crude oil containing emulsified aqueous solutions of inorganic salts, particularly those of calcium, in order to effect separation of oil and water. The briny solution upon contacting the heated metallic surfaces deposit a substantial portion of their mineral content upon said surfaces in a form of insoluble calcareous formations. Consequently, in order to maintain reasonable efficiency of the heaters and to obviate burning out of the heater tubes it is necessary to remove periodically the scale formations that have formed. The latter is but one example of many of such operations in the petroleum field alone requiring frequent acidizing treatment of various pieces of equipment made of iron or a ferrous alloy. Also in many chemical processes it is necessary to store or transport acids, such as the common mineral acids, while in contact with ferrous metals. Accordingly, it can be seen that the practical situations necessitating the minimizing or obviating of the corrosive effect acidic materials, especially those of mineral origin, upon ferrous metal surfaces are legion.

It is one of the objects of this invention to provide a process whereby ferrous metal surfaces can be subjected to aqueous acidic environments without the occurrence of an untoward degree of corrosion.

It is a further object of the present invention to provide an acidizing process for the removal of scale formations from ferrous metals while inhibiting the metal surfaces in contact with the acidizing solution from corrosion.

These and other objects of this invention are attained by preparing a heat reaction product of a member of a class of mercapto compounds with various selected organic compounds containing either a basic nitrogen or amino group and utilizing said product by incorporating ferrous corrosion inhibiting amounts thereof into an aqueous acid solution.

I am aware that the art has hitherto suggested that mercapto compounds as a class, and additionally that various amino compounds, are capable of inhibiting ferrous metal corrosion. However, I have found that when certain members of these respective classes of compounds are combined to yield a heat reaction product, surprising results are obtained in that the products so produced exhibit markedly superior corrosion inhibition than can be observed for either of the reactants per se.

As might be expected, the concept of metal corrosion inhibition is a relative one. Thus, the true criterion of the efficiency or applicability of a particular material to serve as a suitable inhibitor is whether the material will perform satisfactory in relatively small amounts. In the artdirected to the prevention of metal corrosion, it is a practical requisite that any acceptable corrosion arrester be capable of inh biting in rather small amounts. This is especially so because of the economics oftentimes encountered in many acidizing operations such as in the conditioning of oil well piping and the like where it conceivably could be less expensive to use thicker casings as opposed to using large amounts of a chemical inhibitor in the acidizing solution. In this respect, all of the novel inhibitor compositions set forth in the present invention are extremely effective in that they will substantially obviate corrosion of ferrous metals even in the presence of comparatively strong acid solutions in very small amounts, often times in amounts of 1% or less based on the total weight of the acid solution.

The various mercapto compounds useful for preparing the inhibitors for the processes to which this instant invention is directed are: thiol acetic acid, mercapto succinic acid, toluene thiol and ortho-mercapto benzoic acid. The toluene thiols useful in the practice of this invention can be any of the isomeric configurations that can be attributed to this substance. However, with regard to the mercapto benzoic acid, it is preferred that the functional substituents, that is, the carboxylic acid and mercapo groups be in ortho relationship to one another.

The organic nitrogen compounds contemplated as suitable reactants for the above-stated mercapto compounds include a variety of members of various classes of said nitrogen compounds. Suitable among the organic nitrogen compounds are the various 2-alkyl-pyridines. Of the applicable alkyl pyridines, the alkyl group should be in the ortho position relative to the ring nitrogen. The alkyl substituents of the applicable pyridines contain from 4 to 12 carbon atoms. Obviously, mixtures of the various pyridines mentioned may be satisfactorily used. In pointing up the critical nature of each of the types of reactants specifically contemplated herein, it is mentioned that a product derived by reacting picoline, or any of the picolines for that matter, with any of the enumerated mercaptans will not yield satisfactory inhibitors. As a matter of fact, certain of the reaction products of a picoline with one or another of the mercapto compounds enumerated hereinabove will yield products which accelerate corrosion of ferrous metals in the presence of mineral acids rather than inhibit same.

Another suitable class of nitrogen compounds is represented by a series of aliphatic polyamines. I have determined that there is no restriction with respect to the molecular structure of this particular class of nitrogen compounds as was observed for the class of pyridines mentioned. However, especially preferable among the polyamines'are those compounds corresponding to the following formula:

wherein n is an integer preferably 3 or greater. Specific examples of this series of aliphatic polyamines are such as: triethylene tetramine, tetraethylene pentamine, pentaethylene hexylamine, etc.

Particularly suitable organic nitrogen compound or compounds corresponding generally to the above-given formula are the bottoms fraction obtained in the commerical manufacture of various of the polyamines specifioally identified above. The still bottom fractions perform admirably in the practice of this invention, and ad ditionally provide a relatively inexpensive source for this type of reactant.

Another class of aliphatic polyamines which are commerically available and readily adaptable for the uses taught herein are those diamines corresponding to the following general formula:

wherein n represents an integer from about 16 to 18. Exemplary of suitable diamines include a variety of commerical products such as those manufactured by the Armour Chemical Division of Armour Company under the trademark Duomeen. They are a group of fatty diamines of the general formula:

wherein the R represents an alkyl group derived from a fatty acid which is identified as follows:

Duomeen 12; lauric; M.W.=242 Duomeen C; coconut; M.W.=257 Duomeen S; soya; M.W.=321 Duomeen T; tallow; M.W.=320

Alkyl substituted mono amino benzene (aniline) likewise may be used to react with the mercapto compounds set forth hereinabove to produce beneficial inhibitors. The alkyl group of this type of organic nitrogen compound preferably contains from 1 to 6 carbon atom-s. As in the case with the pyridine derivatives, the alkyl substituents of the amino benzene is preferably attached at the ortho position relative to the amino substituent.

Still another class of suitable organic nitrogen compounds is the imidazolines, as represented by the following general formula:

wherein R is either an alkyl or an alkenyl group preferably containing from about 12 to 22 carbon atoms and x represents a substituent containing a replaceable or reactive hydrogen such as hydroxy, amino or imino. These heterocyclic nitrogen bases may be readily prepared by various methods known to those skilled in the art. A particularly preferred method of preparing these compounds consists of reacting a substituted ethylene amine such as aminoethylethyanolamine, ethylene diamine, diethylene triamine, etc. with one of the higher fatty acids such as for example, oleic, stearic, or coconut oil fatty acids, etc.

In illustrating suitable amino nitrogen compounds for reaction with the mercapto compounds to yield the inhibitors useful in the practice of this invention, reference has been largely made to distinct amino compounds. Nevertheless, I have found that mixtures, particularly mixtures of the various organic nitrogen compounds de rived from preparing any of the distinct types mentioned, can be advantageously used for the purposes herein. For example, it bears repeating that any of the still bottoms obtained in preparing the aliphatic polyamines mentioned above make excellent inexpensive co-reactants for the mercapto compound even in spite of their heterogeneous make-up which might possibly include components containing nil or no reactive nitrogen or replaceable hydrogen.

The inhibiting compositions contemplated herein as previously mentioned are the reaction products of a mercaptan such as described with any one of the organic nitrogen compounds enumerated hereinabove. The reaction involved is essentially the formation of a salt of the mercapto compound and the organic nitrogen compound which can be readily accomplished simply by heating these respective reactants at elevated temperatures for various lengths of time. Applicable reaction temperatures range from as low as 65 C. to above 200 C. or even higher. The upper limit of temperature is primarily All.

dictated by the volatility of the particular types of reactants utilized. I have found that a particularly suitable temperature at atmospheric conditions is in the order of C. The time required to effect reaction or salt formation also can be varied over wide limits depending upon the particular temperature utilized, the nature of the specific reactants among other factors and can be noted in most instances when there is a subsidence of evolved gases. Accordingly, a suitable time ranges from about 30 minutes to 4 hours or even longer.

As indicated, the primary reaction involved in preparing the inhibitors of this invention is generally that of salt formation. However, I can not be sure Whether a limited degree of another type or types of reactions occur and in some instances the main reaction that takes place is not clearly understood. Accordingly, I prefer to empirically refer to the reaction product as being one which is heat induced in view of the fact that in many instances .the resultant product defies precise chemical characterization. This is obviously particularly so say where one of the reactants consists of undetermined composition such as the organic nitrogen materials derived from still bottoms in the preparation of polyamines.

Suitable amounts of the respective reactants is represented by approximately equal molar amounts. However, this relation can be varied extensively depending, for instance, upon the number of functional groups contained by either of the reactants. Thus, where the organic nitrogen compound contains a plurality of amino substituents and the mercapto reactant is mono functional, a relatively high molar ratio of mercapto reactant to amino compound can be employed. Conversely, when a mercapto compound such as mercapto succinic acid is reacted with an appropriate pyridine, smaller molar ratios of the acid with respect to the base can be used. With these considerations in mind, the proportions of the respective reactants usually range from about 0.7 to 0.3 mole weight of the mercapto compound and correspondingly from about 0.3 to 0.7 mole of the organic nitrogen compound.

The amounts of the inhibiting composition or reaction product useful in the practice of this invention can be based on the total weight of the aqueous acidic liquid contacting the ferrous metal surface desired to be protected. Thus, from about 0.1 to 5% of the inhibiting composition is employed with the applicable minimum amount being dependent upon the nature of the acid involved, the concentration thereof and the degree of protection sought. Preferably, an amount of inhibiting composition is used corresponding to about 1% or less based on the total weight of the acid solution.

In acidizing procedures, hydrochloric acid solutions from about 10 to 15% strength are generally employed. While hydrochloric acid is particularly favored for this purpose, other strong mineral acids such as sulfuric and the like can be used. In such acidizing solutions from about 0.1 to 5% of the inhibiting compositions of this invention can be added to substantially obviate any corrosive effect that these solutions have upon ferrous metals. Here specifically a preferred amount of my inhibitors also range from about 0.1 to 1%.

In order to further show those skilled in the art how the present invention is practiced, the following specific examples are given in which all parts are parts by weight unless otherwise indicated. These examples are given primarily by Way of illustration and any enumeration of details contained therein should not be interpreted as a limitation on the case except as indicated in the appended claims.

EXAMPLE I Into a suitable reaction vessel equipped with a thermometer, stirrer and a provision for venting to the atmosphere were charged equi-molar amounts of thiol acetic acid and a mixture of alkyl pyridines, the alkyl substituents of the latter ranging in carbon chain length from 4 to 12, with an indicated average of 6.

With stirring, the mixture was heated to about 80 C. and held in the order of this temperature for approximately one hour. The reaction mixture was then discharged from the reaction vessel and cooled to room temperature. The product upon cooling was a viscous liquid capable of being readily dissolved in acidic aqueous systems.

EXAMPLE II Into a reaction vessel equipped as in Example I were charged one part of mercapto succinic acid and one part of an alkyl pyridine mixture identical in composition to that utilized in Example I.

The charged ingredients were rapidly heated to 150 C. and held at this temperature with stirring for approximately 1 /2 hours, whereupon the reaction product was discharged from the vessel and allowed to cool to room temperature.

EXAMPLE III Into a suitable reaction vessel equipped as in Example I were charged one part of mercapto succinic acid and one part of Z-heptadecenyl-l-hydroxyethyl imidazoline. The charged ingredients were heated to 150 C. and held at that temperature with stirring for 2 hours. The reaction product was then discharged from the vessel and cooled to room tempertaure and designated inhibitor IIIa.

An inhibitor was prepared in a similar manner as above from one part of toluene thiol and one part of 2-heptadecenyld-hydroxyethyl imidazoline and was designated inhibitor 11112.

An inhibitor made following the procedure outlined initially in this example from one part of o-mercaptobenzoic acid and one part of the above imidazoline was designated inhibitor IIIc.

EXAMPLE IV An inhibitor was made in substantially the manner in dicated in the previous examples by reacting one part of a polyamine correspondingly generally to the following formula:

where n represents an integer between about 3 and 6 obtained as a bottoms fraction in the manufacture of polyamines and one part of toluene thiol. The resultant reaction product was designated inhibitor IVa.

Another inhibitor (IVb) was prepared by reacting one part of the polyamine of this example with one part of o-mercapto-benzoic acid.

EXAMPLE V An inhibitor composition was prepared by reacting one part of toluene thiol with one part of a diamine mixture corresponding to the following formula:

R 2)3 2i R=C12 to 15 in substantially the same manner described in the previous example.

EXAMPLE VI A heat reaction product (50 minutes at 110 C.) was prepared substantially in accordance with the procedure set forth in the previous examples from one part of toluene thiol and one part of mixed toluidines consisting predominantly of o-toluidine.

EXAMPLE VII Equal parts of a mixture of picolines (o, m, p) and o-mercaptosuccinic acid were reacted at about 90 C. for approximately one hour.

EXAMPLE VIII This example illustrates the effectiveness of the various reaction compositions described in the previous examples as acid corrosion inhibitors. The test for corrosion efliciency was determined by utilizing an aqueous hydrochloric acid solution obtained by diluting 37.5% HCl with 5% aqueous NaCl solution in a ratio of 50:50, respectively. To various portions of the solution was added 1% by weight of the reaction products described in the previous examples. Into each inhibited solution was submersed a freshly abraided 1020 mild steel coupon of a predetermined area (1" x 8" by about A"). Each coupon was exposed in the respective solution for one hour in a static condition. At the end of the exposure period, the coupon was removed, cleaned, dried and weighed. After the weight of the exposed coupon was ascertained, a calculation for determining the effectiveness of the particular inhibitor expressed in terms of percent protection was made. The basis for these determinations was that corrosion (loss of weight) observed for a coupon exposed in a similar manner in an uninhibited acid solution, which basis was considered to be 0.0% protection.

1. An acidizing process for the removal of calcareous incrustation from a ferrous metal surface whereby corrosion of the metal substrate is inhibited which comprises contacting said incrusted surface with an aqueous solution of a strong mineral acid containing from about 0.1 to 5% of the product obtained by reacting at a temperature between about 65 C. and 200 C. from about 0.7 to 0.3 mole of a mercapto compound selected from the group consisting of thiol acetic acid, mercapto succinic acid, toluene thiol, and o-mercapto-benzoic acid, with correspondingly from about 0.3 to 0.7 mole of an organic nitrogen compound selected from the group consisting of a Z-alkyl-pyridine, the alkyl group of which contains from 4 to 12 carbon atoms, an o-alkyl-aniline the alkyl group of which contains from 1 to 6 carbon atoms, a polyethylene polyamine, a N-alkyl-trimethylene-diamine in which the alkyl group is derived from a fatty acid, and an imidazoline substituted in the number one position with an aliphatic group containing a radical selected from the class consisting of hydroxy, amino and imino and substituted in the number two position with a O -C hydrocarbon group selected from the class consisting of alkyl and alkenyl.

2. An acidizing proces for the removal of calcareous incrustrations from a ferrous metal surface whereby corrosition of the metal substrate is inhibited which comprises contacting said incrusted surface with an aqueous solution of hydrochloric acid containing from about 0.1 to 5% of the product obtained by reacting at a temperature between about 65 C. and 200 C. from about 0.7 to 0.3 mole of a mercapto compound selected from the group consisting of thiol acetic acid, mercapto succinic acid, toluene thiol and o-mercapto-benzoic acid, with correspondingly from about 0.3 to 0.7 mole of an organic nitrogen compound selected from the group consisting of a Z-alkyl-pyridine, the alkyl group of which contains from 4 to 12 carbon atoms, an o-alkyl aniline the alkyl group of which contains from 1 to 6 carbon atoms, a polyethylene polyamine, a N-alkyl-trimethylene-diamine in which the "alkyl group is derived from a fatty acid, an

an imidazoline substituted in the number one position with an aliphatic group containing a radical selected from the class consisting of hydroxy, amino and imino and substituted in the number two position with a (E -C hydrocarbon group selected from the class consisting of alkyl and alkenyl.

3. A process according to claim 2 wherein said mercapto compound is thiol acetic acid and said organic nitrogen compound is a 2-alkyl-pyridine containing from 4 to 12 carbon atoms in the alkyl substituent.

4. A process according to claim 2 wherein said mercapto compound is o-mercapto succinic acid and said organic nitrogen compound is a 2-alkyl-pyridine containing from 4 to 12 carbon atoms in the alkyl substituent.

5. A process according to claim 2 wherein said mercapto compound is o-mercapto succinic acid and said organic nitrogen compound is an imidazoline corresponding to the following formula:

where n represents an integer greater than 2.

8. A process according to claim 2 wherein said mercapto compound is toluene thiol and said organic nitrogen compound is a diamine corresponding to the following formula:

where n represents an integer greater than but less than 19.

9. A process according to claim 2 wherein said mercapto compound is toluene thiol and said organic nitrogen compound is o-toluidine.

10. A process according to claim 2 wherein said mercapto compound is o-mercapto-benzoic acid and said organic nitrogen compound is an imidazoline corresponding to the fololwing formula:

in which R is a member selected from the group consisting of alkyl and alkenyl radicals containing from 12 to 22 carbon atoms.

11. A process according to claim 2 wherein said mercapto compound is o-mercapto-benzoic acid and said organic nitrogen compound is a polyamine corresponding to the following formula:

where n represents an integer greater than 2.

12. A process for inhibiting corrosion of ferrous metals in contact With an aqueous acid solution which comprises adding to said solution a corrosion inhibiting amount of the product obtained by reacting at a temperature between about 65 C. and 200 C. from about 0.7 to 0.3

mole of a mercapto compound selected from the group consisting of thiol acetic acid, mercapto succinic acid, toluene thiol and o-mercapto-benzoic acid, with correspondingly from about 0.3 to 0.7 mole of an organic nitrogen compound selected from the group consisting of a 2-alkyl-pyridine, the alkyl group of which contains from 4 to 12 carbon atoms, an o-alkyl aniline, the alkyl group of which contains from 1 to 6 carbon atoms, a polyethylene polyamine, a N-alkyl-trimethylene-diamine in which the alkyl group is derived from a fatty acid, and an imidazoline substituted in the number one position with an aliphatic group containing a radical selected from the class consisting of hydroxy, amino and imino and substituted in the number two position with a C -C hydrocarbon group selected from the class consisting of alkyl and alkenyl.

13. A process according to claim 12 in which said mercapto compound is thiol acetic acid and said organic nitrogen compound is a 2-alkyl-pyridine containing from 4 to 12 carbon atoms in the alkyl substituent.

14. A process according to claim 12 in which said mercapto compound is o-mercapto succinic acid and said organic nitrogen compound is a Z-alkyl pyridine containing from 4 to 12 carbon atoms in the alkyl substituent.

15. A process according to claim 12 in which said mercapto compound is o-mercapto succinic acid and said organic nitrogen compound is an imidazoline corresponding to the following formula:

N (summon in which R is a member selected from the group consisting of alkyl and alkenyl radicals containing from 12 to 22 carbon atoms. 7

16. A process according to claim 12 in which said mercapto compound is toluene thiol and said organic nitrogen compound is a 2-alkyl-pyridine containing from 4 to 12 carbon atoms in the alkyl substituent.

17. A process according to claim 12 in which said mercapto compound is toluene thiol and said organic nitrogen compound is a polyamine corresponding to the following formula:

where n represents an integer greater than 2.

18. A process according to claim 12 wherein said mercapto compound is toluene thiol and said organic nitrogen compound is a diamine corresponding to the following formula:

where n represents an integer greater than 15 but less than 19.

19. A process according to claim 12 wherein said mercapto compound is toluene thiol and said organic nitrogen compound is o-toluidine.

20. A process according to claim 12 wherein said mercapto compound is o-mercapto-benzoic acid and said organic nitrogen compound is an imidazoline corresponding to the following formula:

N HZCI-I OH in which R is a member selected from the group consisting of alkyl and alkenyl radicals containing from 12 to 22 carbon atoms.

21. A process according to claim 12 wherein said mercapto compound is o-mercapto-benzoic acid and said organic nitrogen compound is a polyamine corresponding to the following formula:

Where n represents an integer greater than 2.

References Eited by the Examiner UNITED STATES PATENTS Prutton 260-501 Blair et a1. 252-855 Gardner et al 260-2948 Pennino 260-2948 Riggs 252-855 Hughes et a1. 252-855 Levin 252-855 Eberhard 252-855 Dinsmore et al 260-501 JULIUS GREENWALD, Primary Examiner.

JOSEPH R. LIBERMAN, Examiner. 

1. AN ACIDIZING PROCESS FOR THE REMOVAL OF CALCAREOUS INCRUSTATION FROM A FERROUS METAL SURFACE WHEREBY CORROSION OF THE METAL SUBSTRATE IS INHIBITED WHICH COMPRISES CONTACTING SAID INCRUSTED SURFACE WITH AN AQUEOUS SOLUTION OF A STRONG MINERAL ACID CONTAINING FROM ABOUT 0.1 TO 5% OF THE PRODUCT OBTAINED BY REACTING AT A TEMPERATURE BETWEEN ABOUT 65*C. AND 200*C. FROM ABOUT 0.7 TO 0.3 MOLE OF A MERCAPTO COMPOUND SELECTED FROM THE GROUP CONSISTING OF THIOL ACETIC ACID, MERCAPTO SUCCINIC ACID, TOLUNE THIOL, AND O-MERCAPTO-BENZOIC ACID, WITH CORRESPONDINGLY FROM ABOUT 0.3 TO 0.7 MOLE OF AN ORGANIC NITROGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OF A 2-ALKYL-PYRIDINE, THE ALKYL GROUP OF WHICH CONTAINS FROM 4 TO 12 CARBON ATOMS, AN O-ALKYL-ANILINE THE ALKYL GROUP OF WHICH CONTAINS FROM 1 TO 6 CARBON ATOMS, A POLYETHYLENE POLYAMINE, A N-ALKYL-TRIMETHYLENE-DIAMINE IN WHICH THE ALKYL GROUP IS DERIVED FROM A FATTY ACID, AND AN IMIDAZOLINE SUBSTITUTED IN THE NUMBER ONE POSITION WITH AN ALIPHATIC GROUP CONTAINING A RADICAL SELECTED FROM THE CLASS CONSISTING OF HYDROXY, AMINO AND IMINO AND SUBSTITUTED IN THE NUMBER TWO POSITION WITH A C12-C22 HYDROCARBON GROUP SELECTED FROM THE CLASS CONSISTING OF ALKYL AND ALKENYL. 